Approximate recovery of coseismic deformation from Taiwan strong-motion records |
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| Authors: | Yih-Min Wu Chien-Fu Wu |
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| Institution: | (1) Department of Geosciences, National Taiwan University, No. 1, Sec. 4th, Roosevelt Rd., Taipei, Taiwan, Republic of China;(2) Central Weather Bureau, Taipei, Taiwan, Republic of China |
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| Abstract: | Since 1990, digital strong-motion accelerographs and global positioning system (GPS) instruments have been widely deployed
in the Taiwan region (Shin et al. 2003; Yu et al. 2001). The 1999 Chi-Chi, Mw 7.6 earthquake and the 2003 Chengkung, Mw 6.8 earthquake were well recorded by both digital accelerographs
and GPS instruments. These data offer a good opportunity to determine coseismic displacements from strong-motion records and
to compare the results with those derived from GPS measurements. As noted by Boore (2001), a double integration of the acceleration data often leads to unreasonable results, and baseline corrections are therefore
required in most cases before the integration. Based on the works of Iwan et al. (1985) and Boore (2001), we developed an improved method for baseline correction and validated it using an extensive set of data from shake-table
tests of a known “step” displacement on 249 accelerographs. Our baseline correction method recovered about 97% of the actual
displacement from the shake-table data. We then applied this baseline correction method to compute coseismic displacements
from the strong-motion data of the Chi-Chi and Chengkung earthquakes. Our results agree favorably with the coseismic displacements
determined by the GPS measurements at nearby sites. The ratio of seismic to geodetic displacement varies from 0.78 to 1.41,
with an average of about 1.05. |
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| Keywords: | strong-motion record GPS coseismic deformation baseline correction |
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